Propeller pitch control



Nov. 27, 1951 'r. B. MARTIN 2,575,619

PROPELLER PITCH CONTROL Filed Jan. 17, 1946 Y 2 SHEETS-SHEET 1 IN V EN TOR.

T. B. MARTIN PROPELLER PITCH CONTROL Nov. 27, 1951 2 Sl-IEETS--SHEET 2 Filed Jan. 17, 1946 INVENTOR fin 6 777% BY WJQWM ATTORNEY! Patented Nov. 27, 1951 PROPELLER PITCH CONTROL Thomas B. Martin, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich.,' a

corporation of Delaware Application January 17, 1946, Serial No. 641,758

8 Claims. (01. 170-16021) This invention relates to the control of bladeangle of a variable pitch propeller and more particularly a propeller having hydraulically operated blade-adjusting torque units operated by fluid-pressure means located entirely within the propeller hub.

An object of the invention is to provide means forming a part of the propeller hub assembly for effecting adjustments in accordance with the setting of a device located external to the hub and connected mechanically with said means. The device may be one which is under direct manual control by the pilot or it may be an engine-speedresponsive or engine-torque device mounted, for example, on the engine frame.

In the disclosure and embodiment of the present invention this object is accomplished by providing distributing valve units located within the propeller hub and comprising a valve body having an inlet port connected with a pump also located within the hub and connected with a reservoir of hydraulic fluid provided by the hub. The valve body has distribution ports connected with the torque units and a movable valve member for controlling the distribution port. valve member is under control by the device external to the hub for causing the valve to move away from neutral position to effect a blade angle change and the valve is under control by the blades for returnin the valve to neutral position when the blades have been adjusted to the angle determined by the device.

Further objects and advantages of the present invention will" be apparent from the following description, reference being bad to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is a perspective view, somewhat diagrammatic, showing a propeller and a hydraulic system which includes the present invention;

Fig. 2 is a fragmentary view partly in section on the line 2--2 of Fig. 1;

Fig. 3 is a fragmentary sectional view on the line 3-3 of Fig. 2;

Fig. 4 is a sectional view on line 44 of Fig. 2;

Fig. 5 is a fragmentary sectional View on line 5-5 of Fig. 2; and

Fig. 6 is a fragmentary view in the direction of arrow 6 of Fig. 5.

The blade-angle torque units with which the present invention is adapted tobe used may be, for example, like those disclosed in the patents to Blanchard and MacNeil Nos. 2,307,101 and 2,307,102, issued January 5, 1943. Fig. 1 ShoWS The somewhat diagrammatically a propeller hub and torque unit assembly of the type disclosed in these patents. From the engine frame E there extends an engine driven shaft I which supports and drives a propeller hub 2 which supports an accumulator 3 containing a piston 4 movable toward the right from the position shown under the action of compressed gas forced into the accumulator through a check valve 5. The space, between the piston 4 and the fixed wall 6 of the accumulator, receives oil under pressure which forces piston 4 toward the left further to compress the gas to the left of the piston, thereby maintaining a supply of oil under pressure for the purpose of feathering and unfeathering the propeller blades. Duct 1, through which oil flows into the accumulator, is controlled by a valve to be described.

The hub 2 supports a plurality of blades to, each having its root journaled in bearings ll. Each blade is rotated about its root axis by a separate torque unit comprising a cylinder I2 attached to a blade root and having its upper end closed by cap l3 rotatably supported at its lower end by a bearing l4. Cylinder l2 cooperates with a piston I 5 having external helical splines l6 cooperating with internal helical splines I! of the cylinder [2 and having internal helical splines cooperating with external helical splines is of a relatively fixed member I!) supported by the hub 2. Pipes 2D and 2| lead respectively to the inner and outer ends of the cylinders l2 and are connected in a manner to be described with a distributing valve. The spiral splines are so constructed that inward movement of the piston I5 efiects rotation of the cylinders l2 (clockwise looking outwardly) for the pitch increasing function; and outward movement of the pistons l5 effects rotation of the cylinders l2 in opposite direction for the pitch decreasing function. The cylinders l2 are each connected with a bevel gear segment 22, each meshing with a master gear 23 supported by a bearing 24 carried by the hub 2, thereby equalizing the pitch changin movements of the blades.

The hub 2 supports a plate 30 which, as shown in Fig. 3 is secured by tubular nut 3|. The plate 30. and its cover 32 (Fig. 1) provides a reservoir for hydraulic fluid. The engine shaft l is surrounded by a non-rotatable tube 33 concentric with the shaft and with the nut 3| (Fig. 3). Tube 33 is provided with a tang 34 (Fig. 1) received by nuts between brackets 35 attached to engine frame E. The-plate 30 and its cover 32 provide bearings which maintain the concentricity of the tube 33, one of these bearings being shown at 36 in Fig. 3. Each bearing has a seal such as 31. Tube 33 provides an annular flange 38 which supports a plurality of shafts 39 each driven by a pinion 49 meshing with a ring gear 4| rotatably supported in any suitable manner by the sleeve 33. Ring gear 4| is provided with a handle or lever Me which may be operated by a setting device which is under direct manual control or by one which is automatic in operation such as disclosed in the copending application of Joseph Stuart III, Serial No. 632,566, filed December 3, 1945.

Rotation of gear 4| by lever 4|a effects rotary movements of shafts 39 for the purpose of obtaining blade pitch change. Each shaft 39 provides a screw 45 threaded into a grooved ring 46 slidably along the tube 33. Ring 48 receives a shoe 41 (Fig. 2) attached to a rod 48 guided for movement parallel to the shaft by the plate 39. Shoe 41 connected by screw 49 with a bar 59 having a slot which receives a shoe 52 provided by a pin 53 which swivels in a carriage 54 supported by rollers 55 slidable in ways provided by chan* nel brackets 59 attached by screws 51 to a valve body 58 attached by screws 59 to the plate 39. The valve body 58' is part of a distributing valve unit 69 comprising a valve BI slidable in a valve sleeve 62 having ports 63, 65 and 61 connected by annular grooves 54, 66 and 68 respectively with holes 69, I9 and II respectively. Hole I9 is connected in a manner to be described with a pressure pump. Hole 69 is connected with passages 2| and hole II is connected with passages 29. The position of valve BI is determined by the position of carriage 54 which carries a roller I2 engageable with a lever I3 pivotally supported by pin I4 carried by a screw I5 attached to the valve body 58. Lever I3 is provided with a notch I6 receiving a pin 'I'I attached to the valve 6|. Since centrifugal force acts upon the valve 6| as indicated by arrows 6Ia, Fig. 3, the lever I3 remains in engagement with the roller I2 while the propeller hub is rotated. Hence, no spring is required to hold the lever I3 against the roller I2.' In the disclosed apparatus, when ring gear 4| is rotated counterclockwise by a setting device connected with lever 4Ia, an increase of blade angle is effected. Pinions 49 and shafts 39 rotate counterclockwise thereby causing the grooved ring 46 to move toward the left, thereby moving the carriage 54 toward the left. As roller I2 moves toward the left centrifugal force causes-the valve 6| to move upwardly thereby connecting holes I9 and 69 which causes pressure fluid to flow through pipes 2| in order to force the piston I5 inwardly whereby blade pitch is increased. While the blades I9 are being rotated about their root axes in the direction of pitch increase the valve BI is being returned to a balanced position closing ports 63 and 61 at which position the valve arrives when the demand for pitch increase has been satisfied. In order to accomplish this, the master bevel gear 23 is connected with a gear 89 (Fig. 5) which is retained by a plate 8| attached to the hub 2 and which meshes with a gear 82 pivotally supported by a screw 93 attached to a plate 84 supported by hub 2. Gear 82 meshes with gear 85 attached to a shaft 86 having a bearing and a boss 81 integral with the plate 84. Shaft 86 is connected with a coupling disc 88 connected by a screw 89 with a coupling disc 99 attached to a shaft 9| journaled in a' bearing 92 carried by the plate 39 and retained by a nut 93 threaded on the bearing 92 as shown in Fig. 5. Shaft 91 provided with a helical groove 95 which receives a ball 99 carried by a member 91 which serves as a nut and travels along the helical or screwthreaded groove 95. Nut 91 provides a stud 98 passing through a 'slot 99 in bar 59 and retained by a nut I99. The back lash in the gears 82 and 85 is taken up by spring I9| having one end received by a notch I92 inthe boss 8! and the other end received by notch I93 in the hub of the coupling disc 88. The spring |9| is initially wound up in order to spring-load the gears 89, 82 and 85. Coupling screw 89 passes through an elongated arcuate hole 99a in the disc 99, there by providing for angular adjustment between the coupling disc 88 and 99.

When carriage 54 is in the position shown in Fig. 3 and in full section lines (Fig. 4), the valve BI is in neutral position blocking ports 63 and 6'! so that the torque units will not operate. One set of conditions which places valve 6| in neutral position, is that which exists when screw 49 and stud 98 are located as shown in Fig. 4. These are the conditions for minimum positive or maximum negative pitch. To decrease pitch negativel and increase pitch positively, gear 4| is rotated counterclockwise thereby causing ring 46 and carriage 41 to move left from the position shown in Fig. 2. The demand for pitch increase, positively, may be such as to place screw 49 in position 49' and bar 59 in position 59' and carriage 54 in position 54 (Fig. 4) This will effect blade angle increase, positively, in the manner described. During blade angle increase, the master gear 23 rotates counterclockwise as indicated by arrow 23a in Fig. 1 or clockwise in Fig. 6 as indicated by arrow 23b. Therefore the shaft 99 will rotate clockwise in Fig. 6, thereby causing the screw to rotate counterclockwise as indicated by arrow 95a when viewed from'the direction of arrow 952) (Fig. 5). Therefore, while the blades are being rotated to increase pitch, the nut 91 will be moving down in Figs. 4 and 5 thereby carrying the stud 98 to the position 98' which causes the carriage 54 to be brought back into position shown in full lines in Fig. 4 thereb returning the valve 9| in balanced position. If the movement of ring 46 had been such as to cause the screw 49 to move to 49", the carriage 54 would have been moved further than 54' thereby demanding a greater blade angle change which would cause the stud 98 to move to 98" before the valve BI is returned to balanced position. It is therefore apparent that for every position of the ring 49 there is a definite blade angle. Consequently, for every position of lever 4|a, there is a definite blade angle position. The mechanism shown provides for adjustment of blade angle in a range of approximately The flange 38 of sleeve 33 (Fig. 1) provides a stationary gear H9 meshing with a gear III which drives a pump P while the propeller hub is rotating. The outlet of pipe p of pump P is connected with the passage I9 of the distributing valve 69. Pipe 10 is connected by pipe n with a pressure control unit PC connected by pipe pa with an accumulator control valve unit AV. The pressure control unit PC comprises a valve rod I39 having a dashpot head |3| received by a cylinder I32 connected with pipe 101 and urged outwardly by centrifugal force acting in the direction of arrow I33 and by spring I34 in opposition to fluid pressure acting upon the lower (in Fig. 1) surface of a piston valve-I35 received by a cylinder I36 and controlling a relief port I3'I. Th? inner end of cylinder I39 is connected by pipe I38 with pipe 2| as shown also. Valve I35, being responsive to centrifugal force, causes the pressure in line 12 to increase as speed increases and this pressure is increased also when cylinder I36 receives pressure from the pipe H which is under pressure when there is a demand for pitch increase.

The unit PC includes also a minimum pressure control valve provided by a rod I40 having lands HI and I42 for controlling the connection between port I31 and a discharge port I43. The rod I40 has a dashport head I44 engaged by a spring I45 located in a cylinder I46 connected with cylinder I32. The force of spring I45 is opposed by the fluid pressure acting upon the under (in Fig. 1) side of valve land MI. The pressure available in pipe p will be limited to a minimum value by movement of rod I40 to a position for connecting the ports I31 and I43, valve I35 having opened port I31. Up to a certain rotative speed of the hub, the pressure is limited to a minimum value in order that the accumulator will be fully charged within a short time even while the engine is operating at low speed. This minimum pressure is sufficient for the pitch-decreasing function of the torque units. As propeller speed increases, valve I35, being under control by centrifugal force, requires greater line pressure to cause the opening of the port I31. Therefore the pressure increases in pipe p above the minimum in order to make available, the pressures required for the pitch-increasing function which requires greater pressure with increase of speed.

While rod I40 of unit PC is shown parallel with rod I30 which is under the action of centrifugal force, it will be understood that rod I40 is not controlled by centrifugal force but is actually located at right angles to rod I36. The units PC and AV are fully described in the copending application of David A. Richardson, Serial No. 613,563, filed August 30, 1945.

For the understanding of the present invention, it is sufficient to state that the accumulator control valve unit AV has a check valve I50 which normally blocks flow from the accumulator 3 to pipe 171. When feathering is required, ring 46 is moved to the extreme left to cause a roller I5I (carried by a shoe I52 received in the groove of ring 46) to engage cam I53 on a lever I54 and to effect outward movement of said lever and of a rod I55 thereby opening the check valve I 50. Pressure oil then flows from the accumulator to underside (in Fig. 1) of a piston I55 thereby effecting the opening of a valve I51 so that the accumulator may discharge to pipe 711 through a by-pass around the check valve. During this discharge the valve I5! is held open by oil pressure against the underside (in Fig. l) of a piston I58. As feathering is completed, the pressure difierential between the pressure in pipe 111 and the pressure against the underside of piston I58 decreases and spring I59 closes valve I51. Cam I53 having been momentarily contacted by roller I5I during movement of ring 46 to the extreme left, check valve recloses. Therefore discharge of the accumulator is prevented until it is desired to use accumulator pressure to assist in the unfeathering operation. This is effected by right (in Fig. 1) movement of ring 46 which efiects momentary opening of check valve I50; and discharge of the accumulator into pipes p1 and p takes place.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might. be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. Pitch-setting apparatus for a variable pitch propeller comprising a propeller hub, blades rotatably supported thereby for pitch-adjustment, an hydraulic servo-motor rotatable with the hub for angularly adjusting the blades said servomotor having a cylinder, and pressure-fluid supply and control apparatus rotatable with the hub, said apparatus comprising a fluid-containing reservoir, a pump for forcing fluid from the reservoir to the servo-motor, a distributing valveunit comprising a body providing an inlet port connected with the pump and outlet ports connected respectively with the ends of said cylinder and a valve for controlling distribution from the inlet port to the outlet ports, a valvepositioninglever, supports respectively connected pivotally with the ends of said lever, a mechanism operatively connecting an intermediate portion of said lever with the valve, one of said supports being movable in one direction relative to the other support to effect movement of the valve from outlet-port-closing position in order to obtain a required blade-angle adjustment, the other of said supports being movable in the opposite direction relative to the first support in order to return the valve to outlet-port-closing position when the required adjustment of blade angle has been made, means responsive to the angular movement of the'blades for so moving the second-mentioned support, and means nonrotatable with the hub for actuating the firstmentioned support.

2. Pitch-setting apparatus for a variable pitchpropeller comprising a propeller hub, blades rotatably supported thereby for pitch-adjustment, an hydraulic servo-motor rotatable with the hub for angularly adjusting the blades said servo-motor having a cylinder, and pressure-fluid supply and control apparatus rotatable with the hub, said apparatus comprising a fluid-containing reservoir, a pump for forcing fluid from the reservoir to the servo-motor, a distributing valve unit comprising a body providing an inlet port connected with the pump and outlet ports connected respectively with the ends of said cylinder and a valve for controlling distribution from the inlet port to the outlet ports, a valve positioning lever, supports respectively connected pivotally with the ends of the lever, a carriage pivotally connected with an intermediate portion of the lever, a cam follower supported by the carriage, a lever connected with said valve and providing a cam engaging said cam follower, one of said supports being movable in one direction relative to the other support to effect movement of the valve from outlet-port-closing position in order to obtain a required blade-angle adjustment, the other of said supports being movable in the opposite direction relative to the first support in order to return the valve to outlet-port-closing position when the required adjustment of blade angle has been made, means responsive to the angular movement of the blades for so moving the second mentioned support and means non-rotatable with the hub for actuating the first-mentioned support.

3., Pitch-setting apparatus for a variable pitch propeller comprising a propeller hub, blades rotatably supported I thereby for pitch-adjustment, a hydraulic servo-motor rotatable with the hub for angularly adjusting the blades said servo-motor having a cylinder, and pressure-fluid supply and control apparatus rotatable with the hub, said apparatus comprising a fluid-containing reservoir, a pump for forcing fluid from the reservoir to the servo-motor, a distributing valve unit comprising a, body providing an inlet port connected with the pump and outlet ports connected respectively with the ends of said cylinder and a valve for controlling distribution from the inlet port to the outlet ports, a valve-positioning lever, supports respectively connected pivotally with the ends of said lever, a mechanism operatively connecting an intermediate portion of said lever with the valve, one of said supports being a shoe movable in one direction relative to other support to effect movement of the valve from outlet-port-closing position in order to obtain a required blade-angle change, the other of said supports being movable in the opposite direction relative to the shoe in order to return the valve to outlet-port-closing position when the required adjustment of blade-angle has been made, means responsive to the angular movement of the blades for so moving the second mentioned support, a ring non-rotatable with the hub and having a groove for receiving said shoe, and means nonrotatable with the hub for laterally moving the ring.

4. Pitch-setting apparatus for a-variable pitch propeller comprising a propeller hub, blades rotatably supported thereby for pitch-adjustment, an hydraulic servo-motor rotatable with the hub for angularly adjusting the blades said servo-motor having a cylinder, and pressure-fluid supply and control apparatus rotatable with the hub, said apparatus comprising a fluid-containing reservoir, a pump for forcing fluid from the reservoir to the servo-motor, a distributing valve unit comprising a body providing an inlet port connected with the pump and outlet ports connected respectively with the ends of said cylinder and a valve for controlling distribution from the inlet port to the outlet ports, a valve-positioning lever, supports respectively connected pivotally with the ends of said lever, a mechanism operatively connecting an intermediate portion of said lever with the valve, one of said supports being movable in one direction relative to the other support to effect movement of the valve from outletport-closing position in order to obtain a required blade-angle adjustment, the other of said supports being a nut which is movable in the opposite direction relative to the first support in order to return the valve to outlet port closing position, rotatably supported screw engaged by said nut which, being pivotally connected with said lever, is non-rotatable relative to the screw, means for rotating the screw in response to angular movement of the blades in order to move the nut and thereby to return the valve to inlet-port-closing position when the required adjustment of blade angle has been made, and means non-rotatable with the hub for actuating the first-mentioned support.

5. Pitch-setting apparatus for a variable pitch propeller comprising a propeller hub, blades rotatably supported for pitch-adjustment, an hydraulic servomotor rotatable with the hub for angularly adjusting each blade, each servo-motor having a cylinder and a double acting piston, a master gear effecting the equal movement of all blades, pressure-fluid supply and control apparatus rotatable with the hub and adapted to rotate the blades in either direction, said apparatus comprising a fluid-containing reservoir, a pump for forcing the fluid from the reservoir to either side of the servo-motors, a distributor valve-unit for controlling the distribution of fluid to one side or the other of the servo-motor pistons, means for moving the valve from an equilibrium position to a position admitting fluid to either side of the servo-motor pistons in order to obtain a required blade-angle adjustment, and means interengaging with the master gear and responsive to movement of the blades for returning the valve to the equilibrium position, the means for moving the valve comprising a remotely shiftable support, a lever connecting the support with the valve at an intermediate part of the lever, a nut and screw supporting the other end of the lever, said interengaging means being adapted to shift the last named support.

6. Pitch-setting apparatus for a variable pitch propeller comprising a propeller hub, blades rotatably supported for pitch-adjustment, an hydraulic servomotor rotatable with the hub for angularly adjusting each blade, each servo-motor having a cylinder and a double acting piston, a master gear effecting the equal movement of all blades, pressure-fluid supply and control apparatus rotatable with the hub and adapted to rotate the blades in either direction, said apparatus comprising a fluid-containing reservoir, a pump for forcing the fluid from the reservoir to either side of the servo-motors, a distributor valve-unit for controlling the distribution of fluid to one side or the other of the servo-motor pistons, means for moving the valve from an equilibrium position to a position admitting fluid to either side of the servo-motor pistons in order to obtain a required blade-angle adjustment, and means interengaging with the master gear and responsive to movement of the blades for returning the valve to the equilibrium position, the means for moving the valve comprising a cam carried lever pivotally supported and articulated to the valve so as to respond to centrifugal force, a manually movable cam follower normally engaging the cam carried lever for opposing valve movement by centrifugal force, and a differential lever connected at an intermediate point with said cam follower, and one end of said differential lever being mechanically connected for movement by said master gear and interengaging means.

7. Pitch-setting apparatus for a variable pitch propeller comprising a propeller hub, blades rotatably supported for pitch-adjustment, an hydraulic servomotor rotatable with the hub for angularly adjusting each blade, each servo-motor having a cylinder and a double acting piston, a master gear efiecting the equal movement of all blades, pressure-fluid supply and control appa ratus rotatable with the hub and adapted to rotate the blades in either direction, said apparatus comprising a fluid-containing reservoir, a pump for forcing the fluid from the reservoir to either side of the servo-motors, a distributor valve-unit for controlling the distribution of fluid to one side or the other of the servo-motor pistons, means for moving the valve from an equilibrium position to a position admitting fluid to either side of the servo-motor pistons in order to obtain a required blade-angle adjustment, and

means interengaging with the master gear and responsive to movement of the blades for returning the valve to the equilibrium position, the interengaging means comprising a gear train meshing with the master gear, a relatively movable nutand screw driven by the master gear, and

9 difierential leverage means connecting the nut with the said distributor valve.

8. Pitch-setting apparatus for a variable pitch propeller comprising in combination, a hub, a plurality of blades journalled in said hub for pitch shifting movement, a fluid pressure source provided by said hub for altering the pitch position of the blades, fluid servo-motors actuating each blade, a master gear efiecting equalized pitch change movement of all of the blades, a distributor valve for connecting the fluid pressure source with all of the servo-motors, and means for shifting the distributor valve in either direction from an equilibrium position for actuating the servomotors in reverse directions to effect a desired blade angle change, said shifting means including a cam-carrying lever articulated to said distributor valve and a cam manually movable from a point outside of the propeller for resisting movement of the valve by centrifugal force from the equilibrium position, and follow-up means including a gear train meshing with the master gear 10 for returning the distributor valve to the equilibrium position when the blades shift in angular position to the selected angle determined by th said manually movable cam.

THOMAS B. MARTIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,990,814 Castro Feb. 12, 1935 2,051,837 Fischel Aug. 25, 1936 2,243,852 Caldwell et al -1 June 3, 1941 2,391,699 Haines et al Dec. 25, 1945 2,424,559 Drake July 29, 1947 2,462,932 Anderson Mar. 1, 1949 FOREIGN PATENTS Number Country Date 560,522 Great Britain Apr. 6, 1944 

